Passive vs Active Monitors and monitor amps

[analag]

OK, active monitors are a no no in my studio, also store bought power amps don't cut it. BJT only power amps at that, MOSFETs won't do.  Mono blocks only, well I wound one primary and dual secondaries to run separate P.S.  so mono blocks on the same chassis. BJT working well below their SOA is sweet to my ears.  Gin and tonics guys, Merry new year!

 

[sodderboy]

And to you a wassail too!

 

[ruffrecords]

I used to be set in my ways like you. I would only listen on Tannoys via a decent BJT power amp. Now the scales have fallen from my ears after I bought a pair of JBL LSR305 speakers. Active with built in class D amps they sound absolutely divine. Depth, clarity and bass response far better than I have heard in a long time.

Cheers

Ian

 

[john12ax7]

Why are active monitors a no no? Solves lots of problems.

 

[abbey road d enfer]

OK, active monitors are a no no in my studio, also store bought power amps don't cut it. BJT only power amps at that, MOSFETs won't do.  Mono blocks only, well I wound one primary and dual secondaries to run separate P.S.  so mono blocks on the same chassis.

Your post would be sensible if you explained why... In absence of rational explanation, this is only unproductive ranting.

 

[living sounds]

My misgivings WRT to active monitors are not so much about the amps (modern Class D amps can indeed be very good), but about the active buffers and filters used. Even in expensive  professional monitors they often employ rather mediocre op amps and are usually powered by noisy switching PSUs. An external Hypex Class D amp and a passive monitor using only coils, resitors and capacitors appears to be more beningn or at least less potentially damaging to the signal to me.

But then most monitors today are fed via sigma-delta converters that impart their own "sonic signature" on the signal. And most monitors today are ported and are thus compromised WRT to impulse response.

 

[clintrubber]

Nice coincidence this thread.

I saw those Adam Audio monitors (T7V or T5V, both 2-way active), entry level but lots of bang for buck according to the reviews (...)

"All the connections are on a steel rear panel, behind which is a Class‑D power
pack delivering 20 Watts for the tweeter and 50 Watts for the woofer, crossed over
at 2.6kHz. This is all handled by a Texas Instruments TAS5754M combined amp and DSP chip."

Interesting... back in the day Philips had the 'one-chip TV', now there's the 'one-chip active monitor'... and why not.

I figure they use the 2 power sections of that TAS5754M in BTL for bass, so need another driver for the 20W treble section though.

 

[JohnRoberts]

I used to design and sell active speaker crossovers back in the 80s (before Peavey), I even rolled a few DIY speakers, but for decades now I prefer to have actual professional loudspeaker engineers design active crossovers for the speakers they also designed. Inexpensive class D amps makes self contained bi-amp and tri-amp boxes more practical and cost effective.

Of course some powered boxes are just an exercise in cost cutting... Customers pretty much refuse to factor in the combined price of stand alone amps with speakers when pricing powered boxes, but given the opportunity the engineer with control over all the levers can do a superior job.

JR 

 

[pucho812]

Why are active monitors a no no? Solves lots of problems.

When I first got my start in California, I worked at Westlake Studios. It was then all one company with the studios, the sales division, the manufacturing division, etc all owned  by their chief speaker designer Glen Phoenix.  I once asked him " why doesn't Westlake make a powered monitor?" While I do not remember the entire lengthy discussion, the main idea was that they didn't sound right. That you can use a cabinet to do so much more acoustically when you do not have an amp in the middle of it.    While  they still do not make a powered monitor,  I can attest to how good some of their small bookshelf speakers have terms of frequency response. When we used to show off the small bookshelf speakers that had a 6.5" woof and a 1" doom tweeter, we often had people asking where the sub was because they were unable to believe we had that good a bass response from such a small speaker. 

Fast forward to now and convince will win out. Powered monitors now days sound pretty good over all, even with class D amps, they are not bad.  We use them and get results we like so why not?

 

[john12ax7]

That makes sense, if the acoustics of the enclosure is compromised. My initial thinking was of the benefits of active crossover and short speaker wire.  So perhaps the ultimate is a combo of both.  Separate amps,  with active crossover,  physically close but not inside the speaker cabinet.

 

[JohnRoberts]

If the amp inside is added by the speaker designed (s)he can account for the box volume.

JR

 

[abbey road d enfer]

.  I once asked him " why doesn't Westlake make a powered monitor?" While I do not remember the entire lengthy discussion, the main idea was that they didn't sound right. That you can use a cabinet to do so much more acoustically when you do not have an amp in the middle of it. 

To me, it seems like a delusive answer, hiding the fact they were probably not proficient enough in power amp design.
Making amps is a (relatively) heavy industry compared to speakers (not the chassis, the finished product).

 

[gyraf]

Lately, there is much more to the story than cross-over optimization: New predictive models of speaker behavior includes a whole bunch of dynamic response- and distortion parameters, all of which can be pre-compensated in DSP before going into power amplifier. Which means that you can't any longer separate amplifier and speaker.

Jakob E.

 

[JohnRoberts]

Just to be clear combining the amp into the speaker does not have to literally mean putting the amp inside the box, while that is most convenient, some prefer to bolt the amp to the back of the box. The power of the combination is bringing the amp under the control of the speaker design engineer.

While pre-distorion is a possible benefit, I had mainly seen that used to compensate for throat distortion in large PA horns (the very high SPL inside a high power horn can cause non-linear behavior from the air from being squeezed that hard).  A perhaps more obvious benefit (that I saw executed last century) is making the self powered speakers harder to kill.  Intimate knowledge of power handling and access to the individual drivers allows protection tailored to the components involved.

Another feature is ability to correct for power compression in drivers. As driver voice coils heat up their resistance increases, meaning they receive less power from the same voltage drive. Of course this only offers diminishing returns as you drive it harder to compensate for sagging output it heats up even more. 

====

I wouldn't be surprised to hear about advanced features like mimicking favorite amp distortion sound for some fringe market.

----
For studio monitors accuracy is only part of the design goal. Last time I messed with marketing studio monitors (last century) we used a two position voicing switch to select between one voicing to use for critical listening when laying down tracks, and a second voicing for mix down that better reflected the audience playback speaker response. DSP offers an even broader palate of possible loudspeaker voicing to select from. 

JR

 

[abbey road d enfer]

While pre-distorion is a possible benefit, I had mainly seen that used to compensate for throat distortion in large PA horns (the very high SPL inside a high power horn can cause non-linear behavior from the air from being squeezed that hard).

That was a big topic in the late 90's. A lot of work was done by Wolfgang Klippel, who finally had to give up because his particular solution would require too much DSP power. It may not be true anymore, but in the meantime he changed direction and designed a loudspeaker evaluation system that is now recognized as the ultimate, somewhat akin to Audio Pre for electrical measurements.
His target for his pre-correction system was high-end PA; to my knowledge, today no recognized speaker manufacturer uses it.

A perhaps more obvious benefit (that I saw executed last century) is making the self powered speakers harder to kill.  Intimate knowledge of power handling and access to the individual drivers allows protection tailored to the components involved.

Indeed. Many loudspeaker systems today incorporate some kind of thermal protection. Some, but not many include excursion protection, which is not a so-well understood subject. DSP engineers have just about no clue about it; that's why generic loudspeaker processors are so inadequate in this regard.

Another feature is ability to correct for power compression in drivers. As driver voice coils heat up their resistance increases, meaning they receive less power from the same voltage drive. Of course this only offers diminishing returns as you drive it harder to compensate for sagging output it heats up even more. 

It's always been an issue; each designer has his own take on this. Either play it safe and you protect too early or you let the system reach its limit and then turn-off sharply.
Enzo Ferrari used to say: if you break the engine before the finish line, you've been imprudent; if the engine works after the finish line, you've been too prudent.

 

[JohnRoberts]

That was a big topic in the late 90's. A lot of work was done by Wolfgang Klippel, who finally had to give up because his particular solution would require too much DSP power. It may not be true anymore, but in the meantime he changed direction and designed a loudspeaker evaluation system that is now recognized as the ultimate, somewhat akin to Audio Pre for electrical measurements.
His target for his pre-correction system was high-end PA; to my knowledge, today no recognized speaker manufacturer uses it.

https://www.facebook.com/groups/733449990043427/permalink/1726268357428247/

Here is a video of a panel of leading speaker/horn designers.  Indeed this is a big dog sound reinforcement PA area. (Some obscure inside humor from the industry design leaders.)

David Gunness is the poster boy for modern horn DSP correction (aka "Gunness correction"). Tom Danley (on that same panel) does some remarkable work with unconventional novel horn designs. I believe I read somewhere that David designed his own DSP platform to support his novel algorithms.

Indeed. Many loudspeaker systems today incorporate some kind of thermal protection. Some, but not many include excursion protection, which is not a so-well understood subject. DSP engineers have just about no clue about it; that's why generic loudspeaker processors are so inadequate in this regard.

LF excursion is pretty well understood by loudspeaker design engineers, but not by end users who prefer dealing with simple power or voltage protection thresholds. After I quit Peavey I momentarily considered making and selling stand alone speaker protection boxes that would go between amps and systems while sensing the speakers and using that data to implement protection.  I abandoned it as too difficult to support end users also lacking good data on speakers innards, and measurement points. This really screams to be implemented completely inside powered boxes.  To do this right you need to know the speaker driver parameters, crossover alignment, and cabinet tuning.  Almost impossible to do externally and certainly too difficult for unsophisticated end users.

It's always been an issue; each designer has his own take on this. Either play it safe and you protect too early or you let the system reach its limit and then turn-off sharply.

Indeed different strategies... like I already offered, correcting for power compression can lead to even more heating. Smartest strategies neck back to some lower power limp-along mode (like broken cars that let you drive home.)

Enzo Ferrari used to say: if you break the engine before the finish line, you've been imprudent; if the engine works after the finish line, you've been too prudent.

Big money live sound reinforcement, does not tolerate complete system failures well... I bet*** most high end professional powered sound reinforcement cabinets already use sophisticated protection.

JR

*** I have been out of the trenches for a couple decades but still have friends working in the industry.

 

[ruffrecords]

Just to be clear combining the amp into the speaker does not have to literally mean putting the amp inside the box, while that is most convenient, some prefer to bolt the amp to the back of the box. The power of the combination is bringing the amp under the con

JR

Indeed, back in the 70s at Neve we had some huge 15 inch Tannoy monitor golds in Lancaster cabinets IIRC, each one with a Quad 50E bolted on the back. They were fitted with castors so they could be moved around easily.

Cheers

Ian

 

[abbey road d enfer]

Here is a video of a panel of leading speaker/horn designers.  Indeed this is a big dog sound reinforcement PA area. (Some obscure inside humor from the industry design leaders.)

Facebook does not want me to reach that link; it steers me back to my own pages.  ???

David Gunness is the poster boy for modern horn DSP correction (aka "Gunness correction").

Yes, I'm familiar with his patents, but I'm not sure there's any commercial product taht actually implements his horn-distortion correction...

  Tom Danley (on that same panel) does some remarkable work with unconventional novel horn designs. I believe I read somewhere that David designed his own DSP platform to support his novel algorithms.

Again, I don't think there's any commercial product yet.

LF excursion is pretty well understood by loudspeaker design engineers,

Yes; the problem is most loudspeaker designers are not DSP designers, and it's more than once that communication between loudspeaker and DSP designers is erratic at best. I'm not a DSP designer,, but I know enough about programming and math to present a DSP programmer with a model he can use.

but not by end users who prefer dealing with simple power or voltage protection thresholds.

Agreed; when you realize that only a small fraction of sound system operators understand about loudspeaker power handling, you have to develop fool-proof systems, which, as you know, are permanently challenged by the level of ingenuity of real fools.

After I quit Peavey I momentarily considered making and selling stand alone speaker protection boxes that would go between amps and systems while sensing the speakers and using that data to implement protection. 

That's more or less what a bunch of companies have tried to do - I believe one of the first was dbx with the Drive Rack; they found out they couldn't get reliable info from speaker manufacturer's (who systematically inflate the power handling specs), unless they developped a close partnership, and finally abandoned all pretence at being compatible with all.

 

[JohnRoberts]

Facebook does not want me to reach that link; it steers me back to my own pages.  ???

here is another url directly from the video  https://www.facebook.com/toastyghost/videos/10156413760353142/ This is from a recent AES show.

Yes, I'm familiar with his patents, but I'm not sure there's any commercial product taht actually implements his horn-distortion correction...
Again, I don't think there's any commercial product yet.

David's company is called Fulcrum Acoustics to exploit his IP..

looks like several majors have adopted his technology in their dsp/amps
https://www.fulcrum-acoustic.com/dsp.html

Yes; the problem is most loudspeaker designers are not DSP designers, and it's more than once that communication between loudspeaker and DSP designers is erratic at best. I'm not a DSP designer,, but I know enough about programming and math to present a DSP programmer with a model he can use.
Agreed; when you realize that only a small fraction of sound system operators understand about loudspeaker power handling, you have to develop fool-proof systems, which, as you know, are permanently challenged by the level of ingenuity of real fools.

15 years at Peavey taught me a little about customer proofing products. 

That's more or less what a bunch of companies have tried to do - I believe one of the first was dbx with the Drive Rack; they found out they couldn't get reliable info from speaker manufacturer's (who systematically inflate the power handling specs), unless they developped a close partnership, and finally abandoned all pretence at being compatible with all.

I haven't played close attention to this over recent decades but participated in numerous discussions on sound reinforcement forums about mapping amp power to speaker power handling... not exactly apples to apples.

The first dbx drive rack was a joke... they didn't even suppress turn-on transients (a big no-no for serious sound reinforcement feeding thousands of watts).  They eventually figured that out, but that class of digital crossovers is still locked into cook-book crossover alignments. L-R being very popular because it is relatively easy and safe. 

I have been ranting for decades now about the lack of a concise definition for "q" in peaking type EQ, routinely used in loudspeaker manufacturer crossover presets, making a tower of babel where factory presets only work accurately on factory dsp platforms, but this is getting off topic.

Working at Peavey we had the luxury of amp designers and speaker designers who could sit in the same room and negotiate solutions.

BUT like I said I've been off that reservation for almost 2 decades.

JR

 

[abbey road d enfer]

here is another url directly from the video  https://www.facebook.com/toastyghost/videos/10156413760353142/

Still doesn't work.

David's company is called Fulcrum Acoustics to exploit his IP..

His horn compensation process is just a dedicated EQ, probably not MP, since he calls it Temporal EQ. It has nothing in common with the distortion compensation system patented (but never exploited commercially) by Klippel, which involved a very complex and power-hungry mapped convolution algorithm.

looks like several majors have adopted his technology in their dsp/amps

Not exactly; he has ported his algorithms, dedicated to his own loudspeakers, on several commercial platforms. This is a quite common partnership, just like the one my company has with LineaResearch, where they have included our own excursion protection algorithm in the DSP machines they OEM for us.

I have been ranting for decades now about the lack of a concise definition for "q" in peaking type EQ, routinely used in loudspeaker manufacturer crossover presets, making a tower of babel where factory presets only work accurately on factory dsp platforms,

I've been fighting the same battle probably for the same time. I've more or less given up, except internally everyone knows they should say "bandwidth" if I'm within hearing distance.